Braking apparatus for motor vehicles



June 17, 1930.- M. LOUGHEAD 1,764,177

BRAKING APPARATUS FOR MO'IYOR VEHICLES originalriled Jan. 8 1925 ssheets-sheet 1 ./Vam/m fozfglead F3 www@ (d m0, QAM, .y Album,

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June17, 1930. A M .LoU-GHEAD 1,764,177

` BRAKING APPARATUS FOR MOTOR VEHICLES original Filed Jan. 8, 1925 sSheets-sheet 2 MINIMUM] June 17, 1930. M. LOUGHEAD 1,764,177

BRAKING APPARATUS FOR MOTOR VEHICLES Original Filed Jan. 8; 1925-5`Sheets-Sheet I5 lPatented June 17, 1930 f vl'JNrral) STATES! PATENToFF-lola;l

IALCULH LOUGHEAD, F DETROIT, MICHIGAN, ABSIGNOB TO HYDRAULIC COI- PAINY,03F DETROIT, MICHIGAN, A CORPORATION OI OAIIZIII'OBCNIA.'Y

' BEARING APPARATUS F03 MOTOR VEHICLES Application med January 8, 19125,Serial No. 1,145. B enewed Hay 8,1987.y

My invention relates to braking ap aratus for .motor vehicles. Itsprincipal lo ject isthe use of the driving power or momentum of thevehicle for' furnishing the power to 5 apply the brakes; thereby makinga greater braking force available and reliving the driver of all butthemere control of the brakes. Another object is to maintain a reservebraking force that may be employed '10 when the motor and vehicle arenot in motion or are movingtoo slowly to generate suilicient brakingpower I contemplate that when a gear pump or other pump is used tobuildup thisl reserve power,the pump will be 'relieved of its load whena predetermined reserve is built up.

A further feature of my invention is that when applied to hydraulicbrakes, the liquid `medium passed to the wheel brakes is also the mediumfor its reserve power. My a paratus is arranged particularly to avoidthe loss' of such liquid medium through the leaks often developed inhighvpressure tanks, gaskets, pipe fittings, and the like. This end isachieved in part by designing the apparatus with a view to eliminatingas many as possible of such elements andA lin part by mounting theseveral eleme ts within a casing which forms the reserve reservoir, so

that whatever of liquid medium leaks out will go into :the reservoir andnot be -lost from the system. l

The foregoing and otherpobjects and advantages of my invention will beset forth in detail in the `following specification dis` -at the wheelswhich may be considered as being taken along the line 2-2 of Figure 1;Figure 3 .isra rear. elevation of the usual transmission housing and.also of the casing of mydevice showing its relation in connectiontherewith, which view may be con'- sidered as being taken on lineofFigure l;

Figure 4 is a-longitudinal vertical section taken on the line 1f-4 ofFigure 3;

vFigure 5 is a transverse section taken on the l1ne5-5 of Figure 4; f

Figure 6 is a longitudinal vertical section .taken on the line 6-.6o-Figure 3;

Figure 7 is a plan sectiontaken on the line 7-7 of Figure 6,'a`nd v y Fire 8 is a horizontal section taken on the 11ne 8--8 of Figure 6 andlooking upwardly.

i Briefly described, my braking apparatus.v

as disclosed inthe drawings vincludes hy draulically actuated brakes onthe wheels of the automobile supplied with a liquid vmedium underpressure from acentral or main compressor. This compressor is operatedby a 'gear pump driven not from the motor but from the drive shaft ortransmission of the automobile. A reservesupply of liquid -under heavyspring tension is automatically maintained in the compressor andtheliquid under pressure assed from the reserve or directly from t` e earpump is controlled by a pedal' operated valve which automaticallyregulates the pressure in the brake line proportionately to the pressurethe driver applies to the pedal. A

In Figure 1 I have shown an automobile chassis having the usual engine10, transmis# sion housing 11, anddrive shaft 12; Each of thefour wheelsis provided with a brake mechanism 413 for actuation by hydraulicpressure, the li uid medium being led to thc several wheelsv y means ofiexible hose 14 and tubing' 15 connecting with .a common pressor17 of myinvention. A The chassis construction and also the construction of thebrake mechanism may be of 'passage' through a T-itting 16 on the com- Yany suitable type, for my' invention is not,

concerned witi their detailsN but with the `improved compressor 17. Apreferred form of brake mechanism, however, is shown in vFigure 2. Eachwheel-carries a brake drum 18, across the open face of which is mountedasta'tmnaryplate 19 fixed to the axle housmg or'steermg knuckle as thecase may be.

. oppositely moving pistons 21, the liquid medium being passed to theinterior of the cyl-- inder between` the opposed pistons 21 by Iconnecting the fiexible hose 14 to communicate with a duct 22. The outerends ofthe pistons bear against the lower ends of the levers 23 whichare pivoted at 24 on a stamped steel bracket 25 extending from thecylinder 20. The upper ends of the levers 23 engage suitable nutsadjustably threaded on shanks 2G secured to the ends of the brake band27. Compression springs 28 urge the ends o'l` the brake bands a. )artand Vnorinally force the pistons inwardly to return the liquid mediumtoI the main cl'nnpressor 17. This type of brake mechanism is more fullydisclosed in my co-pending application, Serial No. 680,292, filedDecember 13, 1923.A

My main compressor 17 isl housed within a casing 30 which is secured bybolts 31 to the left sideof the transmission housing 11. Thetransmission housing 11 is extended rearwardly a little farther than`isusual to house a pair of s iral gears 32 and 33, the first of which is eed to the stub shaft 34 extending rearward v from the transmissionforwardly of the first universal joint 35, while the second gear iskeyed to a vertical shaft 36. The spira-l gears 32 and 33 arecontinually in mesh so that the vertical shaft 36 is rotated wheneverthe automobile is in motion.

The shaft 36 extends downwardly through the cover 37 of the casing 30and to the bottom of a well 38in the casing where the lower end of theshaft is journalcd. An undercut conical throw-off ring 39 is preferablyprovided to revent any of the transmission oil which ubricatesthe spiralgears from passing down the shaft into the casing y 30 and being. mixedwith the liquid medium in the casing.

A gear 40 is keyed tothe lower end of the shaft 36 and a matinggear 41is mounted beside it on a shaft 42. The well 38 is-conformed to theopposed sides of the gears so that they form a` gear pump. A plate 43which forms-a horlzontal continuation of a.

. cylinder casting 44 is clamped by cap screws 45 to the top of the well38 to completethe gear pump housing. A passageway 46 (Figs. 6 and 8)communicates between the bottom of the casing 30 and the intake or lowressure side of the gear pump so that the vuid medium is continuallypumped from tie supply held within the casirg.

` mentioned screws 45. T le forward end f the. cylinder 44 is closed byan integrally cast head 47 while the rear end is left open, terminatingsome distance from the rear wall of the casing. Within the vcasing ismounted a reciprocable piston 48 carrying at its forward end a` floatingcup leather 49. The piston 48 is itself cup-shaped, facing rearwardlyfor the reception ofthe forward end of a heavy compression spring 50.The rear end of the spring 50 is carried in a dished plug 51 threadedinto a suitable opening in the rear wall of the casing.` The back sideof the plug 51 has a centering depression 52 in a hexagonal protuberance53, so that in assembling, a gear pullermay be .employed to pull theplug 51 up to the rear wall where a wrench may bc used to thread it inplacethereby placing a strong initial tension on the compression spring5% The cylinder head 47 carries a suitable sto 54 for contacting thepiston to prevent t a-mage to the cup leather when the piston is in itsinnermost position.

The cylinder vcasting is ribbed along the lower edge of one of its sidesto provide a' sufficient stock for a longitudinal borev 55 which extendsparallel with the cylinder and across the top of the integral plate 43.

An outlet opening"56 extends through the plate from the high pressureside of the gear pump and communicates with the bore 55.

A passageway 57 leads through the wall of the cylinder to connect theforward end of the bore 55 with the interior of the cylinder adjacentthe head 47.v lVhenever the auto-y mobile is in motion the drive shaftwill of course be rotatingand the gear (pump therefore operating.' Theliquid me ium will be pumped from the bottoni of the casing 30A throughthe intake p ssage 46, the outlet 56, the bore 55 and the assageway 57into the cylinder forwardly of the piston to build up pressure thereinand force the piston outwardly against the compression of the heavyspring 50.

In order to prevent breakage by filling.

the (Zylinder with more than its capacity of liqui of its load asquickly as possible, I provide a -rotary valve 58v horizontallyjournaled transversely of the bore 55 and controlled bya snap-overmechanism. When the. valve 58 is in theiposition shown in the drawings,allv of the liquid pumped by the gear pump is confined to essa throughthe bore 55 `into the cylindier. ies when the cylinder 44 has beenfilled with the liquid medium under preure and the piston 48 forcedbackwardly to a redetermined point, the valve 58 is snap wise through 90to its'alternate position where communication with the vbore 55 ischargeopening 59 which is, in fact, merely a rearward continuation of the bore55 and presently described,

Counterclockand in order to relieve the gear pump leads to the liquidsupply inthe'cnasing 30. At such time the gear pump hassubstantially noload other than the incidental friction of Auw liquidmedium. This.liquid medium, ii

weather and t separate.

might be here explained, is preferabliynlihalf alcohol and mixturecomprisinguu d. l Sed y 1 o 1n my. co-

castor oil as more pending application, Serial o. 689,815, filed anuary31, 1924, as this mixture does not congeal to an appreciable extent incold e ingredients do not tend to A ball check valve 60 is inserted -inthe bore 55 to prevent retrogression of the liquid under compression inthe cylindery whlch `might otherwise occur around .the valve 58 when,for example, the cylinder has been pression spring 68-isinterposedbetween thc' pum ed up to its capacity and the automo- A bileeft standing.

That trunnion ofthe valve 58 which-extends toward the )center of thecylinder 44 carries a V-shaped arm 61, the le s of .which carry rollers62 and 63 respective disposed inthe same vertical lane. Ar 64 Yispivoted on the arm 61 y the pivot pinjof the roller 62 and extendsupwardly through a socket shaped aperture 65 in a bracket 66 extendingrearwardly from the upper wall of the cylinder casting 44. The rod 64ear-- ries a sem/ispherical washer 67 izo-operating with the socketshaped aperture 65 slidablyI to pivot` the upper end of the rod. Acomwasher 67 and the arm 61 to complete the snap-over mechanism and holdthe valve 1n its` alternate positions 'on either side of a dead centerbetween the opening 65 and the` axis of the valve 58. The valve isstopped in its clockwise rotation by the lug 69 on the valve armpositioned to Contact the plate 43 which extends from thecylindercasting and' forms the cover for the gear pump housinge and in its'counterclockwise rotation by the roller 63 which likewise contacts the.plate The piston 48 has 'a wide groove 70 ad]a centits open endleavinga marginal bead 71. The roller .62 is in alignment with a verticaltangent to the bead 71 so that when the liquid medium is pumped into thec linder and the piston lforced backwar ly" against the force of thespring 50, the `rear` ward face of the bead 71 enga es the roller 62,swinging the valve until t e roller has Vpassed its dead center relationwhen the spring 68 will snap the valve through the rest of its movementto its alternate position where the gear pump pumps the liquid d1-`rectly into the casing. My purpose inema bead 71 rather. than a lug toene snap-over mechanism is that 1i' avoids the necessit ofany means forpre- Playing1 'venting rotation o the piston. In my coin- \pressor^thepiston is `free to rotate 1f the flexing of the compression spring 50tends to turn it. y

'Y When the valve'is y in this position the lower roller 63 hasA beenswun upwardly and lies adjacent the forward ace of the bead 471 and inalignment therewith. l When the volume of li uid inthecylinder-decreases, either b t e Aopening ofY the control valve toyadmit 'quid tothe brakes or by a slow leakage through an of the valvesthe piston will move forwar ly and-the bead 71 engage the roller 63rotating the valve counterclockwise (Fig. 4)v until the roller. 62 .hasagain been brouglit past its dead center relation, whereupon the spring68 will snap the valve counterclockwise a suilicient distanceto'shutnoff the by-pass or relief discharge opening 59 and opencommunication through -the bore 55.

- If the brakes are further applied and the piston continuesto moveinwardly, the

sprin 68 will hold the roller 62 against thc' '8'5 wardly while theroller 63 is freed from the Y forwardV face ofthe bead and ridesdownwardly and out of alignment with the path of the bead. The roller 63will then Contact the plate 43 and stop further forward movement oftheroller 62 but the bead 71 will be free to travel forwardly as theroller-63 is then out of its path. The piston may tlerefore if necessarytravel its full distance for-- wardly as shown in Figure 4, but whenthe) cylinder is again pumped up -and the piston moved backwardly, thebead-71 will pass the.

Vintake grooves 73 and 74 respectively, the

latter being in direct communication with the interior of the cylinderthrough an inlet f' opening 74". The upper groove 73 cominunicates wit-hthe atmospheric pressure in the casing through a relief duct- .73. .A`valve piston 75 is slidably' mounted in the bore 72 and is providedintermediate its ends Swit'h eripheral slots 76 communicating withl tilelower end-of the bore 72. A webextends across the valve piston 75 abovethe slots 761to close communication with the bore above the piston`vGross and verticalfdischarge ducts 77 in the' cylinder head lead fromthe bottom of the bore 72 through, the

.A cover plate 37 to the previousl mentioned T-fitting-l for the tubing15W ich leads to the Wheel brakes.-

A light .compression 'spring 78 in `the I bottom of the bore 72 urgesthe valve 75 upardly to its normal ower"end of a guide lposition againstthev ushihg '79 threaded end and the web of the valve into the openupper end of the bore 72. pedal rod 80 is slidably journaled in theIbushing 79, a relatively heavy compression spi-ing 81 being interposedbetween its lower iston 75. The pedal rod 80 extends upwar ly throughthel floor board of the automobile and occupies a. osition preferablynear the accelerator pe al and where the brake -pedal isnow generallylocated. A small assageway 82 preferably leads from the re ief groove73- to the bore 72 above the valve piston 75 so that pressure cannotbuild up therein to increase the pressure of the spring 81.

-'Let us assume that the compressor is 4in its normal position, that is,that the cylinder has .been pum' ed to its maximum capacity. If thedriver epresses the pedal rod 80 with a force of for example,eight'pounds, the

spring 81 will force the piston valve 7 5 downwardly against the tensionof the lightl 4liquid under .placement of the pistons 21. When enoughlspring 78 which, let us say, has a pressure ofa half pound. Thejvalve 75would therefore have an effective downward force of seven and a halfpounds. The piston valve@ will therefore be moved down to the bottom ofthe bore 72 and the .slots 76 moved out of registry with the reliefgroove 73 and into registry with the intake groove 74. The pressureinthe cylinder will then How through the inlet groove 74, thelower artof the bore 72, the discharge ducts 77 ders 20 at the wheel brakes. Itwill be understood that the tubingl and other portions of the brake-lineas well as the space in the cylinders ltween the pistons are at alltimes lfull of the liquid medium and therefore it is only necessary tointroduce the volume of liquid represented by the disliquid has been.passed through the control valve to build up a back pressure sufficientto counterbalance the vseven and a half pounds' pressure on the valvepiston 75 `the latter will be forced upwardly toits inten mediateposition -where it closes communication with the intake groove 74.Should the driver then press the pedal rod '80 alittle harder, the valvesten 75will' be moved downwardl to a lt more liquid to the brakes untiressure was increased to councommunication Y through the dischar 'liefterbalance t e` increased pressure on the -pedal rod. The valve iston`75 would there;-

upn again finda baance. in shutting of 'th the inlet groove/I4.'

' If-the driver lessens the pressure of the pedal rod the' back`pressure vin thebrake' side of the valve'- will 'move the valve pistonto its u per position where its slots 76 regis-4 ter wi 'the reliefgroove 73. Some of the liquid medium will ow vfrom the tubing. 1 5

duct 77 slots 76, reroove 73 and t e reliefducts 73 into the .interiorof the casing 30, `until the casing sup and tubing 15 to the severalcylinf 'a balancev to maintain -the lessened pressure on the brakes. Ifthe driver removes his -foot entirely from the edal rod 80 thelig'htspring 78 will move't e valve piston 75 to its upper positi n and allowthe pressure on the brakes t e relieved through the relief duct 73. Thecompression springs 28 on the wheel brakes of course return the istons21 to their inner positions and force t e liquid medium, `thusdisplaced, back into the .The `valvev58 tends to kec the reserve supplyof liquidmedium in t e cylinder at its predetermined maximum capacity.Under ordinary operating conditions the piston will be in its rearwardposition and the valve 58 turned to pass the liquid directly from thegear pump to the interior of the" casing. ,A forceful application of thebrakes will take suicient liquid from the cylinder to pei-mitthe piston48 to move forwardly far enough to throw the valve't/o its load pumpingposition. l After th's'is done the gear pump will be rotatin ast enoughto ply the necessary liqui `medium to the bra es until the ressurerequired b the contil valve has en built up, and t e reserve held underressure bythe tension s ring 50 need not e used. As soon as the supplyof liquid medium being delivered by Vthe gear pump, the piston 48 willagain, be

forced to vits rearward f osition until the valve 58 sna s to the i lingor 'non-load.

position for e pum emand of the control valve is less than the I Whenthe `automo ile is at rest or movi ing very slowly and especially whenon. a

slight hill, the gear cannot be. relied upon to'furnish thenecessarybraking ower. It

is under such conditions that tie reserve held under pressure by thespring 50 becomes essential. The cylinder -is preferably of a capacityholding enough reserve liquid under ressure to effect several successiveforcefu ap lications of the brakes. The chec valve60 becomes especiallynecess Awhen the automobile is moving rearwar y and the valve 58 is setas shown in Figurev 6 to communicate with the-bor'e 55, or otherwise thegear pum miglitcoinpletely empty the czrfylinder.l n braking a reversemovement o theautomobile the reserve in the cylinder of courseconstitutes the sole braking. power.

, O i'ie feature of my invention-which is particularly -to be notedisthat the driver, iii a lying the brakes, vneed not'take into consieration the of the gear pump, for the brakes. will the preure he exertson the It is also unnecessary for the pe al rod 80. river to considerthe distance through lwhich lie fle- .l

applied in pro ortion to' Q-.Q thepedal rod for the controlling gactorissolely the pressurev applied. The

. diameter of the bore 72 is preferably such vplied to the bra es.

that the pressure to` be exerted on the pedal rod is but a minorfraction'of the correspending pressure built up inthe brakes, but' stilla ressure which a driver' can readily feel and thereb gaugethe forcebeingv apsult in no increase in the pressure ap lied to the brakes;,itwould, however, be on y after v fnumerous successive a plications `ofthe brake at very low spee s of the automobile that the maximum pressureobtainable in the brakes would be less than the highest pressuredemanded by the control valve.

Another 'advantage to be observed is the simplicity of design and. thefacility of assembl of the compressor 1 have shown. Practically all ofthe `moving parts which might vneed adjustment, -inspection orrepair,the valve 58, associated snap-over mechanism and the controlVvalve,-fare mountedl on. the cylinder casting 44 which may be lifted outof the casing 3() by the removal of the cap screws 45.. i For ease indisassembling or removing the compressor, the pedal rod 48O is eferablyointed and r the mating ends held together y a cotterpin 83.

' While I have described this particular embodiment of my invention I donot consider my invention to be limited specifically thereto andcontemplate that many changes may be made therein without departing fromthe spirit or scope of my invention.

What Iclairn is: 4 1. The combination with a motor vehicle, of a brakingsystem therefor comprising a liquid-actuated brake mechanism for one ofthe wheels, a 'reservoir for liquid comprising a cylinder havin aresiliently mounted piston for holding t e liquid therein underpressure, means including a control valve lliquid under pressureconnecting thereservoir and the brake mechanism; a pum andmeanscontrolled by movement of t e Piston for delivering rom the pump tothe reservoir. i 2. A braking system for an automobile comprising, incombination, a wheel brake mechanism, a pump for supplying liquid underpressure thereto,a cylinder, a .springpresse piston mounted therein, avvalve for controlling the flow of liquid from the pum to the cylinder,said valve being controllo by movement of said piston, and passi-agemeans including a control valve for con'- -the mediuminto the reservoirunder ducting Huid under pressure from the cylinder tothe `brakemechanism.

3. The'combination: wi t li amotor vehicle, of a braking system thereforcomprising wheel brakes,4 means forming a source of liquid medium underpressure comprising a reservoir, s ring means for holding under l ingthe medium into 'the reservoir under pressure, and a valve between thecompres sor and the reservoir for automaticallfy maintaining apredetermined amount o liquid under pressure in the reservoir. 9 4. Thecombination with a motor 4vehicle, of a braking system thereforcomprising wheel brakes, means forming a source of liquid medium underpressure comprisin a.,

4.pressure liquid forced into the reservoir, .a compressor driven by the-wheels for pumpreservoir, springv means for .holding uner pressureliquid forced into the reservoir,l a'

compressor driven by the .wheels for pumpmaintaining the giquid in the.reservoir above a predetermined pressure; meansac- .ing the medium,into the reservoir under pressure,aiid a valve between the compres' sorand the reservoir for automatically tuated by the liquid medium foractuating the wheel brakes; and a manually controlled' inthe reservoirwithin redetermined limits, and manually contro led means actuated bysaid :liquid medium for applying. said brakes. i

6. The combination with a motor vehicle,4

of a braking system therefor lcomprising wheel brakes;means forming asource of liquid medium under pressurecoinprising-a reservoir, springmeans for holding under pressure liquid forced thereinto, and acompressor driven by the wheels for pumping ressure; means actuatedbythe liquid me ium for applying the wheelbrakes; and a manuallycontrolled valve for. admitting the liquid medium vunder pressure fromsaid first-mentioned means to said brake apply ing means.

7. A braking system for a motor 'vehicle comprising wheel brakesactuated by liquid pressure, a cylinder having a resilientlyl mountedpiston, means driven b the vehicle wheels forpumping up the piston "witha liquidunder pressure, control means for said pumpin means 'formaintaining a predetermined amount of liquid under pressure ias ` inthelcylinder, and passage means includmounted' therein, passage meansincluding a'control valve between the cylinder and the brakes, passagemeans includin'g'avalve between the compressor and the cylinder, and asnap-over mechanismfor the latter valve actuated b the piston formaintaining the reservoir lled with liquid under pressure.

9. A servo brake mechanism com rising wheel brakes, a compressor driveny the Wheels, a reservoir, a piston resihently mounted therein, passagemeans including a control valve between the cylinderand the brakes,passage means including valve means constituting a check valve forleading liquidV from the compressor to the reservoir, and means actuatedby the piston for controlling the Valve to maintain a body of liquidunder pressure Yin the reservoir.

10. The colnbination with a servo braking system, of a source of liquidunder pressure comprising a casing forming a liquid supply container, agear pump housing formed in the bottomof the casing, a pair of rotarygears therein, a cylinder within the casing, passage means between thepump and the c linder including a valve, a resilientv sprmg for thepiston, and a control mechanism for the valve actuated by the movementof the piston for maintaining a body of liquidv under compression in thecylinder.

11. A liquid pressure supply device for a servo brake mechanismcomprising a compressor, 'a cylinder having a resiliently mountedpiston, passage means including a valve between the discharge side ofthe compressor and the cylinder, a snip-over mechanism for actuating thevalve, and abutments on the piston for engaging the snap-over mechanismto actuate the valve for `maintaining a body of li uid under compressionin the cylinder, thea utments being annular whereby the snap-overmechanism will be actuated regardless of rotar movements of the Vpistonwithin the cylin er.

12.- A liquid pressure supply device for -a fluid-actuated brake systemcomprising a compressor, piston and cylinder members mounted forrelative rotary movement, passage means between the cylinder` member andthe discharge side of the compressor including a valve, a snap-overmechanism for the valve, and annular abutments -on one of said membersfor engaging the snap-over mechanism to maintain a body of liquid underpressure in the cylinder member even though the member carrying theabutments .rotates relatively to the snap-over mechanism.

13. A unitary liquid pressure supplyingalso within the casing, and anintake passage for the compressor incommunication with the interior ofthe casing foi-,carrying into the liquid system any liquid whicheseapesinto the casing from any of the aforesaid elements of vthesystem.

14. The combination with a sei-vo" brake mechanism, of a device forsupplying liquid under pressure thereto comprising a casing having a.gear pump housing ormed in the bottom thereof, rotary gears for the gearpump, a cylinder communicating with the discharge side of the gear pumpmounted within the casing and having a plate portion completing the gearpump housing, and a resiliently mounted piston in the cylinder formaintaining the liquid therein under pressure.

15. A device forming a source of liquid under pressure for afluid-actuated brake system comprising a compressor, a casing, acylinder mounted within the easing and in communication with thedischarge side of the compressor2 a piston in the cylinder, the cylinderhavlng an open end facing toward one wall of the easing, a compressionspring abutting the piston and extending toward said opposite Wall, anopening in the wall opposite the open end of the cylinder for theinsertion of the spring, and an abutment member for ,the outer end ofthe spring screw threaded into said opening for placing an initialtension on the spring.

16. The combination with a motor vehicle of a braking system thereforcomprising wheel brakes, a casing for confining liquid. a reservoirsubmerged in the liquid ot' said casing for holding the liquid forcedthereinto under pressure, a compressor for pumping the liquid from thecasinginto the reservoir under pressure, said compressor being disposedwithin said casing and submerged in the liquid therein, liquid pressureoperated means for applying the brakes and a manually controlled valvefor admitting the liquid underpressure from the reservoir to the brakeapplying means.

17. The combination with a motor vehicle of a braking system therefor,comprising wheel brakes, a casing for confining a liquid medium, 'areservoir submerged in the liquid in said casing'for holding liquidunder pressure, a compressor for pumping liquid under pressure from thecasing into the reservoir,

automatic means including a mechanically actuated valve for maintainingthe pressure in said reservoir v substantially constant, liquid pressureactuated means for applying the brakes, vay nianually cont-rolled valvefor admitting the. liqud under pressure from the reservoir to tho brakeapplying means, and means associated with the valve for re1ev ing backpressure from the brake applying moans to the casing when the valvereturns t'o its inoperative position.

In wit-MSS wl'loreof, I hereunto subscribe my namo this 27th day ofDecember, 1924.

MALCOLM LOUGHED.

